In the art of making tires, it can be desirable to employ rubber vulcanizates that demonstrate reduced hysteresis loss, i.e., less loss of mechanical energy to heat. Hysteresis loss is often attributed to polymer free ends within the cross-linked rubber network, as well as the disassociation of filler agglomerates.
Functionalized polymers have been employed to reduce hysteresis loss and increase bound rubber. The functional group of the functionalized polymer is believed to reduce the number of polymer free ends. Also, the interaction between the functional group and the filler particles reduces filler agglomeration, which thereby reduces hysteretic losses attributable to the disassociation of filler agglomerates. The present application stems from a recognition that an aminosilane (“silazane”) functional group within the polymer portion of a rubber vulcanizate has been found to improve the physical properties of the rubber vulcanizate. The aminosilane functionality in the polymer presumably improves the interaction of the polymer with additional components, such as silica fillers. This improved interaction often translates into improved mixing and better dispersion of ingredients.